Spatial and temporal dynamics of West Nile virus between Africa and Europe

Abstract

It is unclear whether West Nile virus (WNV) circulates between Africa and Europe, despite numerous studies supporting an African origin and high transmission in Europe. We integrated genomic data with geographic observations and phylogenetic and phylogeographic inferences to uncover the spatial and temporal viral dynamics of WNV between these two continents. We focused our analysis towards WNV lineages 1 (L1) and 2 (L2), the most spatially widespread and pathogenic WNV lineages. Our study shows a Northern-Western African origin of L1, with back-and-forth exchanges between West Africa and Southern-Western Europe; and a Southern African origin of L2, with one main introduction from South Africa to Europe, and no back introductions observed. We also noticed a potential overlap between L1 and L2 Eastern and Western phylogeography and two Afro-Palearctic bird migratory flyways. Future studies linking avian and mosquito species susceptibility, migratory connectivity patterns, and phylogeographic inference are suggested to elucidate the dynamics of emerging viruses.

Abrupt Increase in Detection of Locally Acquired West-Nile-Virus-Lineage-2-Mediated Neuroinvasive Disease in a Previously Non-Endemic Area of Southern Italy (2023)

“…The same lineage was identified in mosquitoes and animals [ 17 ]. This lineage was reported in Sub-Saharan Africa and Madagascar, before spreading to Europe, and no genetic flow in the opposite direction was reported [ 4 ]. Currently, in Italy, the circulation of both Lineage 1 and 2 has been documented [ 17 ].…”

“…Currently, Europe has no specific surveillance programs to monitor seroprevalence, and testing is only indicated on clinical suspicion of infection [12]. However, the identification of WNV in animals (i.e., mosquitoes, horses, and birds) requires public health measures to prevent human-to-human transmission through contaminated blood donations [4]. According to the EU Blood Safety Directive, a negative individual donor nucleic acid test, or 28 days of deferral from donation, is required if the donor has returned from areas in which human cases of WNV infection have been detected [13].…”

“…Environmental factors have been considered as potential regulators of the annual incidence rate; in fact, increased temperatures shorten the replication cycle of vectors, and feeding increases accordingly (accompanied by increased biting frequency) [ 3 ]. Symptomatic disease is more common in horses than in humans, and the neuroinvasive form has a mortality rate of 33% [ 4 ]. Human cases are thought to be the tip of the iceberg since most are asymptomatic, and full recovery is usual [ 5 , 6 ].…”

“…At least nine lineages of WNV have been described worldwide, with Lineages 1 (L1) and 2 (L2) being the most prevalent in Europe [ 10 ]. WNV L1 was first introduced from Northern–Western African countries to Italy and France in 1988 and 2000, respectively, while WNV L2 was identified in Hungary in 2004 [ 4 ]; since 2008, it has spread across central Europe and the eastern Mediterranean region, becoming more virulent in vertebrates [ 11 ].…”

Prevalence, Diversity, and Virulence of Campylobacter Carried by Migratory Birds at Four Major Habitats in China

“…Birds can indirectly spread pathogens via feces, by contaminating water, and by carrying ticks, etc. [ 15 , 16 , 17 , 18 , 19 ]. As a typical zoonotic bacterial pathogen, Campylobacter is widely detected and researched in wild and domestic animals, particularly poultry and livestock, such as chicken, pigs, cattle, sheep, and the corresponding food products [ 20 , 21 , 22 , 23 ].…”